1. Field of the Invention
This invention relates to a test element for use in a biochemical analysis apparatus and a test element cartridge containing therein such test elements, and more particularly to a test element for detecting a shift in position of a "dry-to-the-touch" chemical analysis element in the course of transfer thereof in a biochemical analysis apparatus and a test element cartridge containing therein such test elements, the "dry-to-the-touch" chemical analysis element being an element having a reagent layer whose optical density changes upon chemical reaction, immunoreaction or the like with a specific biochemical component contained in a sample liquid such as blood or urine.
2. Description of the Related Art
Quantitative or qualitative analysis of a specific component in a sample liquid is a common operation carried out in various industrial fields. Especially, quantitative analysis of a chemical component or a solid component in body fluids such as blood or urine is very important in the field of clinical biochemistry.
There has been put into practice a dry chemical analysis film with which a specific chemical component or solid component contained in a sample liquid can be quantitatively analyzed through a droplet of the sample liquid spotted on the film. See, for instance, Japanese Patent Publication No. 53(1978)-21677, U.S. Pat. No. 3,992,158, Japanese Unexamined Patent Publication 55(1980)-164356 and U.S. Pat. No. 4,292,272. When such a dry chemical analysis film is used, the sample liquid can be analyzed more easily and more quickly than when a conventional wet analysis method is used, and accordingly the dry chemical analysis film is very convenient for medical facilities, laboratories and the like where lots of sample liquids have to be analyzed.
When quantitatively analyzing the chemical components or the like contained in a sample liquid using such a chemical analysis film, there is used a biochemical analysis apparatus in which the chemical analysis film is taken out from a cartridge and transferred to a predetermined position, a droplet of the sample liquid is spotted on the film, the film spotted with the sample liquid is transferred into an incubator and held therein at a constant temperature for a predetermined time (incubation) so that coloring reaction (coloring substance generating reaction) occurs, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength which is preselected according to the combination of the component to be analyzed (sometimes will be referred to as "analyte", hereinbelow) and the reagent contained in the reagent layer of the film is projected onto the film and the optical density of the film is measured. Then the concentration or the activity of the analyte is determined on the basis of the optical density using a calibration curve or a standard curve which represents the relation between the concentration (content) of the analyte and the optical density. After the measurement, the film is taken out from the incubator and discarded in a discarding box.
In such a biochemical analysis apparatus, the successive processings are effected while transferring the analysis film from position to position. When the analysis film is shifted from a predetermined position on a film take-out means or a film transfer means while it is taken out from the cartridge or transferred, spotting the sample liquid on the analysis film, the incubation, the measurement of the optical density and the like cannot be centered on a predetermined position on the analysis film, e.g., the central portion of the analysis film, which results in a fine difference in the measured value and substantially affects the result of determination. Accordingly, in a biochemical analysis apparatus where the accuracy of measurement is very important, there has been a demand for means for checking whether the analysis film can be held in a predetermined position on the film take-out means or the film transfer means while it is taken out from the cartridge or transferred.